OK, I did it :-) Falling asleep on my chair, 1.30 AM here...
During the next few hours, a package called "sleeper" will show up in extras-devel. It's a very simple widget with two buttons, one "15" and the other "30". Have fun :-)
(If the widget doesn't shop up after you added it to the desktop, please reboot - this only happens if haven't yet installed any pyton-widget before)